Light modulating displays and methods of forming them are well known. Displays can include a substrate, a first conductive layer, a light modulating material, and a second conductive layer. To drive the display, electrical impulses are provided to the first conductive layer and the second conductive layer to form an electric field that acts on the light modulating layer. Various methods of making electrical contact with the first conductive layer are known.
U.S. 2003/0202136 to Stephenson et al. discloses a display in which a polymer dispersed material layer is removed to expose a first conductor, creating a gap in the polymer dispersed material layer. Conductive material is printed over the gap to contact the first conductor, creating a single column contact.
U.S. Pat. No. 6,394,870 to Petruchik et al. describes a method for forming a display. A transparent, electrically conductive coating is formed on a transparent substrate. A light modulating layer including liquid crystalline material in a polymer binder is formed over the electrically conductive layer, and an opaque conductive material is deposited in an imagewise pattern over the light modulating layer in the form of viewable and conductive images. Electrical connections enable an electrical field to be applied between selected ones of the viewable and conductive images and the transparent electrically conductive layer. Electrical connections from a printed circuit board to the first conductor are made through rounded or piercing pins that penetrate the light modulating layer. To facilitate electrical contact of the rounded pins to the first conductor, chemical etching of the light modulating layer is required. However, such etching is undesirable due to complexity and the amount of time required. The piercing pins can damage the conductive layer. Piercing pins are also disclosed in U.S. Pat. No. 6,166,796 to Stephenson.
In U.S. Pat. No. 6,469,757 to Petruchik, a process for selectively removing a light modulating layer containing a liquid crystalline material in a polymeric binder from the electrically conductive layer of a liquid crystal display web is disclosed. The process includes applying to a selected portion of the upper surface of the display web a solvent effective for softening the light modulating layer at a controlled rate of application. The solvent forms a selected, softened portion of the light modulating layer, which is removed from the electrically conductive layer of the substrate. This process can lead to physical damage of the electrically conductive layer, such as scratching, leading to failures in the performance of the display.
There exists a need therefore for providing electrical contact to a first conductor that is simple to implement and avoids damaging the conductive material.